A Plain-Language Glossary of Common Nutrition Terms

Bioavailability

The proportion of a nutrient that the body can actually absorb and use after consumption. A food can be rich in a nutrient on paper, but poor bioavailability means the body may absorb far less than the label suggests. Cooking method, food pairing, and individual gut health all affect bioavailability.

Macronutrients

The three major categories of nutrients the body uses for energy: carbohydrates, proteins, and fats. Macronutrients are measured in grams on nutrition labels and provide calories. Each serves distinct physiological roles beyond simply fueling the body.

Micronutrients

Vitamins and minerals required in relatively small amounts but essential for normal body function. Examples include iron, calcium, vitamin D, and vitamin B12. Unlike macronutrients, micronutrients do not directly provide calories.

Net Carbs

A term — not an official regulatory definition — commonly used in low-carbohydrate diet communities. It typically refers to total carbohydrates minus fiber (and sometimes sugar alcohols), on the rationale that these components have a lower impact on blood sugar. Interpretation can vary by product and dietary approach.

Phytonutrients

Naturally occurring compounds found in plants — including vegetables, fruits, legumes, and grains — that may support health. Also called phytochemicals, they include categories like flavonoids, carotenoids, and polyphenols. Research into their specific health effects is ongoing.

Glycemic Index (GI)

A scale ranking carbohydrate-containing foods by how quickly they raise blood glucose levels compared to pure glucose. A high GI indicates a faster blood sugar response. GI is a useful reference point but has significant limitations when applied to mixed meals or real eating contexts.

Antioxidants

Compounds that help neutralize unstable molecules called free radicals in the body. Vitamins C and E and beta-carotene are common examples. While antioxidant-rich foods are associated with health benefits, high-dose antioxidant supplements have produced mixed results in research.

Dietary Fiber

The indigestible portions of plant foods that pass through the digestive system largely intact. Soluble fiber dissolves in water and can help moderate blood sugar and cholesterol levels; insoluble fiber adds bulk to stool and supports regularity. Most Americans consume less fiber than public health guidelines recommend.

Amino Acids

The building blocks of protein. The body uses twenty amino acids, nine of which are considered 'essential' because the body cannot synthesize them and must obtain them from food. Complete proteins — such as those from animal sources and some plant sources like soy — contain all nine essential amino acids.

Saturated Fat

A type of dietary fat that is solid at room temperature and found primarily in animal products and some tropical oils. Most major health authorities recommend limiting saturated fat intake, though ongoing research continues to examine the nuance of different food sources and their effects.

Electrolytes

Minerals that carry an electrical charge and help regulate fluid balance, nerve signaling, and muscle function. Common electrolytes include sodium, potassium, magnesium, and calcium. They are lost through sweat and must be replenished through food and fluids.

Fortification

The deliberate addition of nutrients to food during processing — often to replace what was lost, or to address widespread population deficiencies. Common examples include iodized salt, vitamin D-fortified milk, and folic acid added to enriched grain products.